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Historic Water Cisterns Restored At San Juan National Historic Site

Historic cisterns at San Juan National Historic Site recently were restored to operating condition and will be used to hold water for non-potable uses at the site. Top photo shows the entrance to one of the cisterns below Castillo San Cristóbal, while the lower photo shows some of the detail from inside one of the cisterns. NPS photos.

A long project that restored a bit of history has been completed at San Juan National Historic Site, where crews have completed restoration of the water cisterns that lie beneath the plazas of Castillo San Felipe del Morro and Castillo San Cristóbal.

The restoration work involved three cisterns with a combined capacity of nearly 250,000 gallons in El Morro and four cisterns with a capacity of more than twice that in San Cristóbal. The water stored in the cisterns will be used for non-potable uses at the fortifications.

The water, harvested from an intricate Spanish-designed rain drainage and storage system throughout the fortifications, will now be pumped out of the cisterns. It is to be used in rest rooms, maintenance facilities, and other non-potable applications. Next year the park plans to complete additional work to provide potable water to all of its facilities, allowing the site to achieve the levels of water conservation practiced in the past.

Rain water harvested in the cisterns was crucial to the survival of the Spanish when building the cisterns in the mid-1700s. The significance of the cisterns was such that religious images were painted on the walls for the protection of their water. U.S. Army personnel, taking over the fortifications after the Spanish-American War of 1898, closed the cisterns as they believed the water had been poisoned by the defeated Spanish soldiers.

Since 1949, when San Juan National Historic Site was established, the cisterns remained
unused until the present, with the exception of one in San Cristóbal. Capturing and using harvested rainwater will enable the park to become more efficient, save money and reduce dependency on municipal water systems.

A brief ceremony was planned for Friday morning to dedicate the restored cisterns.